An internet watchdog has launched a new system as part of ongoing attempts to keep children safe on the web.

Worries about child safety on the net are the number one concern for parents and high-profile cases where children have met paedophiles online have intensified fears in recent years.

Parents have a strong, legitimate concern about what children are doing on the internet

Stephen Balkam, ICRA

The labelling system developed by the Internet Content Rating Association (ICRA) enjoys the backing of some of the world's top sites including Yahoo, MSN and AOL.

The system is designed to give parents control over net content by blocking access to certain sites and chatrooms known to be used by paedophiles.

The filters can be sent to block access to nudity, violence, drug and alcohol promotions.

Parents can download the software free from ICRA's website and can either opt for pre-set filters or set up their own depending on how much freedom they want their children to have.

Choice not censorship

Such filters have been criticised in the past by advocates of net freedom who say it is bringing unnecessary censorship to the web.

ICRA says that its system is about choice and is sophisticated enough to distinguish sites that have educational, artistic or medical content.

"We do not make judgements about what is good or bad," said ICRA chief executive Stephen Balkam. "Parents decide and they have a strong, legitimate concern about what children are doing on the internet."

No filter system could be 100% safe though, he admitted, and such filters were not designed to take the place of parental supervision.

"You wouldn't leave a child wandering around Leicester Square and you shouldn't leave them alone on the web. Computers should not be buried away in the corner of the child's room," said Mr Balkam.

Backed by parents

BTopenworld is the first Internet Service Provider, (ISP), in the UK to sign up for the labelling system.

Vice president Duncan Ingram said they were simply responding to parental demands.

"Security is the biggest issue for parents. The internet is uncensored which is both its biggest strength and its biggest weakness. This is not about censorship but about choice, especially for parents," he said.

ICRA hopes to get the endorsement of every major ISP in the world and 50,000 sites in the UK and the UShave already signed up to the filter scheme.

The filter works by persuading websites to place a cinema-style rating in their source code.

Online paedophile rings are becoming increasingly prevalent. This week two British men were charged with involvement in a sophisticated internet paedophile group calling itself The Round Table.

The group traded thousands of images of child pornography over the net.